No abstract

A hybrid of six (6) 4-hydroxyindole azo compounds was synthesised by the diazotization and coupling strategy via electrophilic aromatic substitution reaction. Characterisation by Infrared and UV-Vis spectroscopic studies was carried out and the antimicrobial activity and structure-activity relationship were explored. Amongst the compounds, 4d was the most active against Pseudomonas aeruginosa than the other organisms from the high-throughput spot culture growth inhibition (HTSPOTi) antimicrobial assay. According to the resistant modulation study, the compounds did not show significant activity against the panel of pathogens used. Furthermore, compounds 4a and 4f inhibited biofilm formation in Pseudomonas aeruginosa and Staphylococcus aureus at 70% (31.25 µg/mL) and 57% (125 (µg/mL) respectively. Additionally, 4c and 4e have biofilm inhibition potential against Pseudomonas aeruginosa and Staphylococcus aureus which are implicated in antimicrobial resistance. Hence, the compounds are promising leads with potential to be developed into new antibacterial agents to combat the menace of antimicrobial resistance.

A library of six compounds with new hybrids in a single molecule triazole ring attached to the phosphonium salts was synthesized. Click chemistry was, however, used to synthesize the 1-, 2-, and 3-triazole intermediates as a tether for the hybrid phosphonium salts. Their antibacterial activity against Gram-positive bacteria (Staphylococcus aureus and Enterococcus faecalis), Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), and Mycobacterium smegmatis mc2155 was determined using the HT-SPOTi assay. Compound 2 showed the most effective antimicrobial activity as it inhibited the growth of Pseudomonas aeruginosa and Staphylococcus aureus at 0.0125 µg/mL and 31.25 µg/mL, respectively. From the FICI data, compounds 2ET-TOL (2) and RABYL-TOL (4) successfully modulated the activities of amoxicillin against Pseudomonas aeruginosa and Staphylococcus aureus. All the test compounds exhibited a concentration-dependent biofilm formation inhibition against S. aureus, except P-Z (compound 6). Compounds P-MEOXY (1) and 2ET-TOL (2) exhibited mild activity against P. aeruginosa with compound 4 showing antimycobacterial activity at 500 µg/mL.